In the search for suitable brake linings for high-performance brake systems using ceramic brake disks, the conventional organically bonded brake lining compositions reach their limits because of the high temperatures and high wear rates which occur. This becomes particularly clear in the case of friction pairings in which C/SiC or C/C—SiC is used as brake disk material. These materials are a ceramic which consists essentially of silicon carbide and secondary phases comprising silicon and carbon and is reinforced with carbon fibers, for example as described in DE-A 197 10 105. These materials are, as is known, produced by infiltration of porous C/C intermediate bodies (carbon reinforced with carbon fibers) with liquid silicon and reaction of at least part of the carbon with this to form silicon carbide. Temperatures of 1000° C. and more occur at the friction surface during braking in the case of such brake disks, which can result in decomposition of organically bonded brake linings.
In DE-A 197 27 587, the problem of the high operating temperatures during braking in a combination of brake disks comprising a short-fiber-reinforced C/SiC ceramic and a brake lining having an organically bonded matrix is solved by the brake disk being designed so that its thermal conductivity perpendicular to the disk surface is at least 20 W/m·K. Due to this high thermal conductivity, it is possible to use conventional, organically bonded brake linings in conjunction with the ceramic brake disk. However, the operating lives which are achieved for the linings are not satisfactory.
DE-A 197 27 586 discloses a combination of a C/SiC brake disk and a corresponding C/SiC brake lining, with the C/C intermediate body of the brake lining having a higher density (lower porosity) than the surface regions of the C/C intermediate body of the brake disk. This leads to a C/SiC having a relatively low strength being formed after liquid silicization of the C/C intermediate body of the brake lining because of its relatively low silicon carbide content. However, the overall frictional and wear behavior, in particular the comfort characteristics, is not yet satisfactory constant friction values are not obtained, the noise during braking is too loud and the performance when wet is unfavorable. DE-A 197 27 585 discloses the combination of a short-fiber-reinforced C/SiC ceramic brake disk and a brake lining comprising a sintered metal material or an inorganically bonded material comprising a ceramic binder phase which is preferably obtainable by complete or partial pyrolysis of at least one preceramic polymer and metal particles. Although this brake lining is able to withstand high temperatures, this system, too, is not yet satisfactory in respect of the braking behavior. DE-A 107 11 830 describes a process for producing friction linings for combination with brake disks comprising fiber-reinforced ceramic, in which a pressed body produced from carbon and metal particles is sintered.
It is therefore an object of the invention to provide friction linings which can be used in combination with friction bodies or friction disks made of ceramic materials, in particular C/SiC ceramic, do not decompose even at high temperatures and offer a constant frictional behavior and good comfort characteristics.